System of control.



K. A. PAULY.

SYSTEM OF CONTROL.

APPLICATION FILED APR. 19, 1910.

1,026,364. Patented May 14,1912.

2 SHEETS-SHEET 1.

mnvz'ssz's/ JHYEAZTUB.

1515' ATIUBHE'x.

K. A. PAULY.

SYSTEM OF CONTROL. APPLICATION IIILED APB.19, 1910.

1,026,364. P Patented May 14, 1912.

2 sHBnTssEnET 2.

Fig. 2.

WiLnesses: Inventor: Karl Paul g, b

' UNITED STATES PATENT oFFIoE.

KARL A. PAUIJY, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK. I

SYSTEM: OF CONTROL.

Specification 01 Letters Batent.

Patented May 14, 19 12.

Applidation filed April 19, 1910. Serial no. ssaasr.

To all whom may concern citizen of the United States, residin at Schenectady, county of Schenectady, tate of New York, have invented certain new and useful Improvements in Systems of Control, of which the following is a specification.

My invention relates to the control of d namo electric machines, and has for its ject the control of the field of such machines when used in conjunction with alternating current motors, My invention is particularly applicable to the speed control of direct current motors used 1n conjunction with, but not mechanically connected to, alternating current motors.

the loa For driving rolling mills induction motors are particularly suitable because of their ruggedness and freedom from commutation troubles, but it is often desirable to adjust the speed of the finishing stands for different kinds of work, and for speed adjustment a direct current motor is better adapted than an induction motor. If, however, a direct current motor is employed for drivin the finishing stand while the rest of the ro ls are driven by induction motors, trouble may arise with varying load, due to relative speed variations between the induction motors and the direct current motors, which -may roduce looping or kling of the steel w ich is being rolled. In-

ductlon motor driven rollinglmills are ordinarily (provided with fly-w eels to reduce fluctuations, which also reduce the speed variations, but, in order to reduce the peak of the load to a minimum without using a fly-wheel of excessivelweight, it is.

essential that the induction motor should 'dropsomewhat in speedasthe load'comes In order to prevent'th'e steel from bucklin as it passes to the finis tions ofthe induction motor for varying the 7 speed of the direct current motor so as to buc- stand,

I provi e means responsive to spec vanareference to the accompanying drawings, in which Figure 1 shows diagrammatically a control system arrangedin accordance with my invention, and Fig. 2 shows diagrammatl- -cally a, rolling mill of a type to which my invention is applicable.

In Fig. 1, A represents the stator or primary member of an induction motor supplied from the three-phase lines. B represents the rotor or secondary member which is provided with collector rings. Through these rings the rotor may be connected to a starting resistance C. D is a small resistance which is left permanently in the rotor circuit. E represents the armature of a direct current dynamo electric machine or motor which mechanically independent of the induction motor and which is supplied with current from the direct current mains e6. F represents a field winding of the direct current motor which I have shown as shunt connected and provided with a rheostalt f by means of which the speed of the motor may be ad'usted. F represents a secondfield winding or the motor, the current in which is varied so as to vary the motor field stren th and the motor speed in accordance wit variations in the speed of the main induction. motor. For varying the current in thefield wind ing F many different arrangements may be employed. In the particular embodiment shown in the drawing I employ rotary transformin apparatus consistmgof an auxiliaryin uction motor G and an auxiliary direct current generator H. This auxiliary generator has itsarmature connected to the eld winding F of the direct current motor and has its-field winding or windings "connected in any suitable way adapted to give the: desired voltage. character stic to the with the armature 'H; Arheostat hrna %Vith the main induction motor up: to

at, be used adjust the strength of-the speed the secondary circuitis closed through the resistance D and the auxiliary induction motor G is connected in parallel to this resistance. The frequency of the alternating current supplied to the primary winding of this auxiliary motor G depends upon the slip ofthe main motor and, consequently, its speed varies directly with the slip of the main motor. Therefore, if the load on the main motor increases and the slip increases accordingly, the speed and voltage of the auxiliary generator H increase, increasing the current in the winding F and thereby strengthening the field of the direct current motor E, so that the speed of the direct current motor is decreased. By properly proportioning the windings of the direct current motor and of the auxiliary direct current generator, proportionality between the speeds of the main induction motor and dlrect current motor may be maintained.

If the auxiliary induction motor and direct current generator are designed to operate at eflicient speeds for ordinary amounts of slipof the main induction motor, itis evident that speed limiting means should be provided for this motor generator set in order to prevent excessive speed in case of abnormal slip in the main motor such as would occur, for instance, if the current in the main motor were thrown off and then were thrown on again after the speed of the main motor had been greatly reduced. Asa speed limiting device I have indicated a circuit breaker J in the 'connectionfrom the auxiliary motor G to the secondary of the main motor. This circuit breaker is provided with a tripping coil 7' connected in shunt to one phase of the secondary of the main motor. The voltage on the termi nals of this trip ing coil rises with an increase in slip o .the main motor. Consequent-ly, 'if the slip of the main motor becomes abnormal the circuit breaker J will be tripped... Y

The coil 9' should be of comparatively high resistance and low reactance so as not to be greatly affected by change of frequency,

which, if the coil were of high reactance and low resistance, would nearly neutralize the change in voltage.

In Fig. 2 I have shown, somewhat diagrammatically, a plan view of a rolling mill of a type to which my invention is appli-. cable. The induction motor A drives the- 1 rolls K through which the steel is as indicated by the dotted line and, in the direction shown by the arrow heads. .The motor is provided with the usual "fly-wheel M. L represents the finishing rolls which are driven bythe direct current motor E. These rolls are 'mechanioalli independent of the rolls K,but bymeans o my invention,

while the speed of these rolls may be adassed justed, it varies automatically with the .those skilled in the art and I aim, in the appended claims, to cover all modifications which are within the scope of my invention.

.What' I claim as new and desire to secure by Letters Patent of the United States, is,

1. In combination, an induction motor, a direct current motor mechanically independent thereof, and means mechanically independent of said motors and responsive to speed variations in the induction motor for varying the field strength of the direct current motor to maintain a proportionality between the speeds of said otors.

2. In combination, an in notion-motor, a directcurrent motor mechanically independent thereof, and means mechanically independent of said motors for maintaining a proportionality between the speeds of said motors comprising an electrically operated apparatus responsive to speedvariatio'ns in the induction motor and controlling the speedof the direct current motor.

3. In combination, an induction motor, a .direct currentmotor mechanically independentthereof, and electrodynamic appa-v ratus connected to a field winding of said direct current motor and supplied with current from the secondary member of said induction motor- 4. In combination, an induction motor, a direct current motor mechanically independent thereof, and rotary transforming apparatus connected on its alternating current side to the secondary member of the induction motor and on its direct current side to a field winding of the direct current m0- tor.

-5. In combination, an induction motor, a

direct current motor mechanically independent thereof, and means for automatically increasing the fieldstrength of-the direct current motor upon a decrease in speed of the induction motor.

6. In combination, an induction motor, a direct current motor mechanically independent thereof, an auxiliary generator connected to afield winding of the. direct current motor, and means for driving said generator at a speed varying directly with the slip of the inductionmotor.

In combination, an induction motor, a direct current motor mechanically inde-* pendent thereof, an auxiliary direct current generator driven at a speed which increases when the speed of the induction motor decreases, an

electrical connections from said j generator to a field Winding of the direct current motor.

8. In comblnation, an induction motor, a

direct current motor-mmechanically independent thereof, an auxiliar enerator connected to afield WindingJo t e direct current motor, means for driving said generator at a speed varying directly with the slip of the induction motor, and means for automatically limiting the speed of said generator.

9. In combination, an induction motor, a direct current motor mechanically independent thereof, rotary transforming apparatus connected on its alternating current side to the secondary member of the induc-' tion motor and on its direct current side. to a field winding of the direct current motor, and speed limiting'means for said apparatus.

10. In combination, an induction motor, a direct current motor mechanically independent thereof, rotary transforming apparatus connected on its alternating current side to the secondary member of the induction motor and on its direct current side to a field winding of the direct current motor, a switch fordisconnectingsaid apparatus from the induction-motor secondary, and an electromagnet in circuit with said secondary controlling said switch.

11. In combination, two interrelated loads an induction motor for driving one of said loads, a variable speed direct current motor for driving the other, and means responsive to spee variations in the induction motor for producin corresponding variations in the speed 0 the direct current motor. I 1

12. In combination, an induction, motor, adirect current dynamo electric "machine, electrodynamic apparatus connected to a field windin of sand direct current dynamo electric mac inc and sup lied with current from thesecondary mem er of said induction motor, and a source of direct current, independent of said electrodynamic apparatus, for supplying the armature of said.

dynamo electric machine.

13-. In combination, an-induction motor,

a direct current dynamo electric machine,

rotary transformer apparatus connected on its alternating current side to the secondary member of the induction motor and on its direct current side to a field winding of the direct current dynamo electric machine, and a source of direct current, independent of said rotary transformer appartus, for supplying the armature of said dynamo electric machine.

14. In combination, an induction motor,

a direct current dynamo electric machine, 7

means for automatically increasing the field strength of the direct current dynamo electric machine upon a decrease in speed of the induction motor, and a source of direct current, independent of said means, for su plying the armature of said dynamo electric machine.

15. In combination, an induction motor, a direct current dynamo electric machine, means mechanically independent of said motor responsive to speed variations in the induction motor for varyin the field strength of the direct current ynamo electric machine, and a source of direct current, independent of saidmeans, for supplying the armature of said dynamo electrlc machine.

In witness whereof, I have hereunto set my hand 18th day of April, 1910.

' Witnesses:

Barnum B..HuLL, Hmmn Our-01m.

KARL A. PAULY; 

